Apparatus for monitoring the radioactivity of a plurality of liquid scintillation samples deposited on multi-well sample plates

ABSTRACT

An apparatus for counting liquid scintillation samples which includes a sample plate containing a plurality of cup-shaped sample wells, a photomultiplier assembly over the tops of said cup-shaped sample wells, a photomultiplier assembly beneath the bottoms of said cup-shaped sample wells and light reflective tubes extending upwardly from said lower photomultiplier assembly and surrounding each cup-shaped sample well.

BACKGROUND OF THE INVENTION

Multi-well sample plates which comprise several separate sample wellsare widely used as test plates for in vitro analysis. Said plates can beproduced for example by vacuum thermoforming (deep drawing) from atransparent plastic sheet and they have for example eight rows of wellsarranged in twelve columns. These plates can be used especially forpreparing typically low energy beta radiation emitting liquidscintillation samples. Unfortunately, these samples must first betransferred into liquid scintillation counting vials, because existingliquid scintillation counters cannot count samples directly from thiskind of multi-well sample plates.

SUMMARY OF THE INVENTION

The present invention shows a new apparatus which counts one or severalliquid scintillation or corresponding samples at a time directly fromthe multi-well sample plates which comprise several separate samplewells.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1a and 1b show vertical sections of the counting apparatus undertwo different conditions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1a a sample plate (10), which has several sample wells (11) isplaced manually or automatically in a position where a liquidscintillation sample (16), which is in the sample well (11), can becounted. In order to count one or several samples (16), which are insaid sample wells (11), at a time, the apparatus has one or severaldetectors that consists of two photomultiplier tube assemblies (14a,14b) which work in coincidence and are situated on the top and bottom ofsaid sample plate (10).

The lower photomultiplier tube assembly (14a) is provided with a tube(12). The inner diameter of this tube (12) is equal to or larger thanthe maximum outer diameter of the sample wells (11).

The apparatus has a moving mechanism, which is not shown here, by whichsaid lower photomultiplier tube assembly (14a) provided with said tube(12) can be moved to up or down positions.

In FIG. 1a said lower photomultiplier tube assembly (14a) provided withsaid tube (12) is in the down position in order to allow free horizontalmovement of said sample plate (10). In FIG. 1b said lowerphotomultiplier tube assembly (14a) provided with said tube (12) hasbeen lifted to the up position tightly against said upperphotomultiplier tube assembly (14b) in order to form an optically closedcompartment around said sample well (11) of the sample plate (10).

In order to guide the light from the liquid scintillation samples (16)located in said sample wells (11) to said photomultiplier tubes (14a,14b), the inner surfaces (17) of said tube (12) reflects or scatterslight.

In order to prevent light from travelling between the sample wells (11)inside the material of the sample plate (10), one or both of thesurfaces (18) between the wells (11) of the sample plate (10) arepainted black or this region (18) is treated in some other way whichprevents light from travelling between the sample wells (11) inside thematerial of the sample plate (10).

The invention is not confined to the above embodiments alone, but it mayshow even considerable variation within the scope of the patent claims.

What is claimed is:
 1. An apparatus for counting liquid scintillationsamples which comprisesa sample plate (10) that contains a plurality ofsample wells (11), each sample well (11) comprising means for containinga scintillation sample and being in the form of a cup having an opentop, a closed bottom and side walls extending upwardly from said closedbottom to said open top, a first photomultiplier tube assembly (14b)that is positionable immediately above the open top of a first samplewell (11), a second photomultiplier assembly (14a) that works incoincidence with said first photomultiplier assembly (14b) and which ispositionable beneath the closed bottom of said first sample well (11), atubular member (12)(a) extending upwardly from said secondphotomultiplier assembly (14a), (b) having an internal diameterapproximating the maximum external diameter of said first sample well(11), (c) completely surrounding the side walls of said first samplewell (11), and (d) having an inner surface (17) that reflects orscatters light so as to guide the light from a liquid scintillationsample that is placed in said first sample well (11) to saidphotomultiplier tube assemblies.
 2. Apparatus according to claim 1wherein the surfaces of said sample plate that extends between saidsample wells are treated to prevent light from travelling between saidsample wells via the material of said sample plate.